Bridge Pier Scour in Clay-Sand Mixed Sediments at Near-Threshold Velocity for Sand

Local scour at circular bridge piers embedded in a clay-sand-mixed bed was investigated in laboratory flume experiments. The effects of clay content, water content, and sand size on maximum equilibrium scour depth, equilibrium scour hole geometry, scouring process, and time variation of scour were studied at velocities close to the threshold velocities for the sand in the clay-sand mixture. It was observed that clay content and water content were the key parameters that effect the scouring process, scour hole geometry, and maximum equilibrium scour depth. The bridge pier scouring process in clay-sand mixtures involved different dominating modes for removal of sediment from scour hole: chunks-of-aggregates, aggregate-by-aggregate, and particle-by-particle. Regression-based equations for estimation of nondimensional maximum scour depth and scour hole diameter for piers embedded in clay-sand mixtures having clay content of <40% and water content of <40% were proposed as functions of pier Froude number, clay content, water content, and bed shear strength.     

Synthesis of carbon nano-fibers on p-Si having improved temperature sensing capability

Synthesis of an innovative material for temperature sensor based on carbon nano-fibers (CNFs) on p-Si substrates has been demonstrated. The CNF films were characterized by SEM, Raman and FTIR studies. First order Raman spectra indicated a G band at ～1597 cm^?1 corresponding to the E_2g tangential stretching mode of an ordered graphitic structure with sp² hybridization and a D band located ～1350 cm^?1 originated from disordered carbon. Gold fingers were deposited on the p-Si/CNF surface for resistance measurement. Temperature sensing properties were also investigated critically. Resistance changes with temperature (ΔR/R) in p-Si/CNF films are found to be significantly large 30–60% Very stable, reproducible and improved temperature sensing properties would make this material superior to commonly available temperature sensors.     

Project network-oriented materials management policy for complex projects: a Fuzzy Set Theoretic approach

This work devises a materials management policy integrated with project network characteristics of complex projects. It proposes a relative quantitative measure, overall criticality (OC), for prioritisation of items based on penalty incurred due to their non-availability. In complex projects, practicing managers find it difficult to measure OC of items because of the subjective factors and intractable nature of penalties involved. However, using their experience, they can linguistically identify the antecedents and relate them to consequent OC. This work adopts Fuzzy Set Theory to capture managerial tacit knowledge which provides them enough flexibility to provide information in real form. Computed OC values can be used for items prioritisation and as shortage cost coefficient in inventory models. The revised materials management policy was applied to a shipbuilding project. OC values were analysed to justify the importance of incorporating project network characteristics and potential cost savings were calculated.     

Supply chain risk assessment during new product development: a group decision making approach using numeric and linguistic data

Companies strive to minimise supply chain related risks during new product development as any glitch while developing new products can lead to considerable delay in product launch with severe financial implications. However, many organisations face difficulty in properly assessing the vulnerabilities of their globally dispersed supply chains during the product development stage as no suitable procedure for that purpose seems to be readily available in the literature. The present research is an attempt to fulfil this requirement. A step-by-step approach for supply chain risk assessment during new product development, involving group decision making, is suggested. This approach can use both numeric and linguistic data and helps in determining vulnerability scores for various sub-systems and for each supplier of the most vulnerable sub-system. This is followed by failure mode effect analysis (FMEA) which helps prioritise failure modes of vulnerable suppliers and thus create specific control plans to mitigate supply related failures. Using this approach, organisations can devise control plans to alleviate the supplier related risks during new product development. Although, the methodology is illustrated through an application in aircraft manufacturing, it can also be used in other discrete and process manufacturing industries.     

A PROCEDURE FOR THE PRODUCTION OF ULTRA-PURE PRECURSORS FROM COAL FOR THE MANUFACTURE OF VALUE-ADDED CARBON PRODUCTS - TREATMENT OF THE RESIDUE

ABSTRACT

Solvent extraction of coal results in a coal-derived extract containing the solvent-soluble organic portion of coal free of almost all mineral matter. A residue is also produced and consists of most of the mineral matter. Although a procedure has been developed to manufacture ultra-pure coke precursors for value-added carbon products from coal-derived extracts, treatment/rc-usc of the residue is necessary to make the process economically attractive and environmentally friendly. In this study, a technique has been developed to beneficiate the residue by specific gravity fractionation. It is found that nearly 70 % of the residue can be separated into a fraction containing less than 3.5% ash for a typical WV bituminous coal using an organic liquid having a specific gravity of 1.5. This treatment enables the residue to serve as a low-ash boiler fuel or a suitable precursor for the manufacture of materials such as activated carbons. Consequently, the potential for coal-derived precursors leading to new and non-conventionai marketable carbon products can be realized easily.     

MILD HYDROCRACKING — A STATE OF THE ART

ABSTRACT

This paper is a brief, but not exhaustive review of the literature of the catalytic mild hydrocracking processes. It includes data characterizing reactivities, reaction network and kinetics of mild hydrocracking reactions. This review is designed for use as a reference for further research and development work in the field of mild hydrocracking.     

Corrosion in Propane Deasphalting Unit in a Lube Producing Refinery: A Case Study

Abstract

Propane deasphalting is a process of recovery of hydrocarbon distillates from vacuum residue by extracting with liquid propane. A plated tower is used to carry out extraction where extract containing the deasphalted oil and raffinate containing the asphalt are separated. Extract and raffinates are then subject to propane recovery sections wherefrom propane is recovered and reused in extraction. Complete recovery of propane from deasphalted oil is carried out by flashing alone, but recovery from asphalt requires heating in a furnace followed by flashing. Severe corrosion has been observed in the propane condensers, coolers, and the overhead lines of the flashers and stripper columns. Studies have indicated that cracking of asphalt at the prevailing operating temperature and pressure, generating hydrogen sulfide, was the sole reason for corrosion. The problem has been minimized by adjusting the temperature and pressure without affecting the propane recovery efficiency.     

A Novel Method of Synthesis of Nanostructured Aluminum Nitride Through Sol‐Gel Route by In Situ Generation of Nitrogen

Nanostructured Aluminum Nitride (AlN) has been prepared by carbothermal reduction followed by nitridation (CTRN) of alumina gel over a temperature range 1200°C–1350°C and time period of 30 min to 3 h. Before heat treatment the gel is repeatedly evacuated and purged with ammonia. The nanopores of the gel are filled with ammonia which acts as a source of in situ nitrogen at heat‐treatment temperature. Dextrose also decomposes at the reduction temperature and generates ultrafine carbon. The stability diagram of the carbon saturated Al–N–O system is constructed and it shows that extremely low partial pressure of oxygen is required for the stability of AlN. The ultrafine carbon as well as hydrogen from the cracking of ammonia is not sufficient to create the extremely low partial pressure of oxygen required for the stabilization of AlN. So the sample is heat treated in charcoal boat in nitrogen atmosphere to achieve an extremely low partial pressure of oxygen required for the formation of AlN. The material has been characterized through XRD, FESEM, and HRTEM analyses. The spherical particle size of AlN is obtained ～21 nm.     

Self-tuning flexible ac transmission system controllers for power oscillation damping: a case study in real time

Design and real-time implementation of a self-tuning flexible ac transmission system (FACTS) controller is illustrated for power oscillation damping. Although the system model is not required for self-tuning control design, it is shown to perform similar to a model-based design. For parameter estimation, the classical recursive least square (RLS) is supplemented by a random walk (RW) with a switched structure and compared to standard variable forgetting factor (VFF) approach. It is shown that the RW improves the accuracy and convergence of the estimated system parameters, which is critical to self-tuning control following large disturbances. The performance is validated in real time using a commercial real-time simulation platform. The control computation time is shown to be considerably less than the typical sampling time used for power oscillation damping applications demonstrating the feasibility of self-tuning FACTS controllers in practice.     

On three-dimensional singular stress/residual stress fields at the front of a crack/anticrack in an orthotropic/orthorhombic plate under anti-plane shear loading

A novel eigenfunction expansion technique, based in part on separation of the thickness-variable, is developed to derive three-dimensional asymptotic stress field in the vicinity of the front of a semi-infinite through-thickness crack/anticrack weakening/reinforcing an infinite orthotropic/orthorhombic plate, of finite thickness and subjected to far-field anti-plane shear loading. Crack/anticrack-face boundary conditions and those that are prescribed on the top and bottom (free, fixed and lubricated) surfaces of the orthotropic plate are exactly satisfied. Five different through-thickness crack/anticrack-face boundary conditions are considered: (i) slit crack, (ii) anticrack or perfectly bonded rigid inclusion, (iii) transversely rigid inclusion (longitudinal slip permitted), (iv) rigid inclusion in part perfectly bonded, the remainder with slip, and (v) rigid inclusion located alongside a crack. Explicit expressions for the singular stress fields in the vicinity of the fronts of the through-thickness cracks, anticracks or mixed crack–anticrack type discontinuities, weakening/reinforcing orthotropic/orthorhombic plates, subjected to far-field anti-plane shear (mode III) loadings, are presented. In addition, singular residual stress fields in the vicinity of the fronts of these cracks, anticracks and similar discontinuities are also discussed.